Impact tools



E. SUSSMAN IMPACT TOOLS May 10, 1966 3 Sheets-Sheet 1 Filed Aug. 13, 1965 New MRR INVENTOR ATTORNEYS E. SUSSMAN IMPACT TOOLS May 1o, 1966 5 Sheets-Sheet 2 Filed Aug. 13. 1963 INV ENTOR w uw@ www BY W/Ev! ATTORNEYS E. SUSSMAN May 10, 1966 IMPACT TOOLS 3 Sheets-Sheet 5 Filed Aug. 13, 1965 @NWN INVENTOR MMM,

A'ITGRNEYS United States Patent O eicient and easily controlled operation for either re-V peated or single action.

The invention in its preferred embodiment contemplates the provision of an impact tool comprising a tubular main casing or body member into the forward end of which is telescopingly introduced a tool shaft or shank carrying within the body member an anvil head, and

onto the rearward end of which is mounted a telescoping cap member which serves the purposes of providing a handle for the tool and for enclosing and operating the power gas capsule.

Within the body member is a hammer-piston and valve assembly which is activated both by the forward pressure of the handle or cap member and by the rearward pressure on the tool shaft when applied to the Work, to etect the tapping of gas pressure from the capsule, to etIect single shot impact, and for repeater operation.

Other objects and features of novelty, including the provision of novel latching means for the hammer, bypass valving in the piston, means providing automatic recoil to repeat condition, pressure-actuated locking means for the cap handle, and release valving for the gas capsule, will be apparent from the following specification when read in connection with the accompanying drawings in which one embodiment of the invention is illustrated by way of example.

In the drawings: FIGURE 1 is a view in longitudinal axial sectio through an impact tool embodying the principles of the invention, the parts being in the positions they occupy when the compressed gas power capsule has just been punctured but the driving piston has not yet moved forwvardly to a cocked position, or in an idle or inoperative position when the capsule has been exhausted;

FIGURE 2 is a similar view with the parts in the positions they occupy when the tool is in cocked condition ready to be pressed upon the point to be impacted;

FIGURE 3 is a similar View with the parts in the position they occupy immediately the tool is pressed against the work;

FIGURE 4 is a similar view with the parts retracted from the initial application position of FIGURE 3 and the tool shaft is about to be driven; the movement during a cycle of repeated operation being intermittently from FIGURE 4 to FIGURE 3 and back to FIGURE 4 until a new supply of compressed gas needs to be tapped from the pressure capsule;

FIGURE 5 is a fragmentary view of the intermediate portion of FIGURE 2 on an enlarged scale;

FIGURE 6 is a transverse sectional view taken on line 6 6 of FIGURE l; and

FIGURE 7 is a longitudinal sectional view taken through the forward portion of the handle-cap member and showing the thread grooves by means of which vthe cap is applied.

Structure In the drawings, one exemplary embodiment of the invention is illustrated and there will be indicated in the specification the preferred materials of which some of the r'ce various parts may be composed, but no unwarranted limitation is to be read into these disclosures since the configuration, construction, and arrangement of the parts may be varied, and diiferent materials employed in their composition, without departing from the scope of the invention as defined by the subjoined claims.

The novel tool has been lgiven the general reference designation 10 and comprises a tubular body 11 which is preferably made of aluminum. Threaded within the forward end of the body portion 11 is the nose member 12 which may also be made of aluminum. Extending through an opening in the nose 12 is the tool shaft 13, to the outer end of which may be secured an impact tool head of any desired nature, such as that indicated at 14. The rear end of the tool shaft or shank 13 is formed as a cylindrical anvil element 15, the central portion 16 of which is narrowed to approximately the diameter of the shank 13 and tted with a slender projecting stem 17. A cylindrical cavity 20 is formed in the inner wall of the body portion 11, which is of somewhat greater axial dimension than the anvil 15 Ato give the anvil some slight axial play for purposes which will be explained hereafter.

The rearward portion of the body member 11 is stepped to form several cylindrical portions of graduated diameters, the first level indicated at 22 slidingly receiving the forward end of the external cap member 25 which functions as a handle for the tool. The next rearward stepped portion of the body member 11 indicated at 26 is threaded for the reception of the internally threaded forward end of the retainer sleeve 27, which sleeve embraces and secures the expansible intermediate pressure gas supply container 30, the construction and function of which will be described presently.

Threaded upon the inal rearward level 31 of the body member 11 is the cup-like' element 32, the cylindrical body portion of which forms a housing for a chamber in the immediate vicinity of a main supply valve member to be described. Extending rearwardly from the cup-like body portion of the member 32 is a tapered valve element 33 from which extends a piercing pin 34 which enters the mouth of the high pressure gas supply capsule 35. The neck of the capsule has an opening with a frustoconical seating portion 36 which together with the similarly tapered portion 33 of the member 32 forms a valve which controls the issue of pressure gas from the capsule 35 under the control of the handle cap Z5.

Guided for axial sliding movement within the cylindrical portion 38 of the body member 11 is the driving and controlling piston 4G, and Screwed into the hollowed forward end of the piston 40 is the hammer portion 42, a small chamber 43 being formed internally of the piston rearwardly of the hammer.

Extending through an axial port or passageway 44 in the piston is the stem 45 of the main supply valve 48, this stem also passing through a wider passageway 46 within the rearward wall of the bodyportion 11, the frusto-conical valve member 48 adapted to seat on a tapered surface 49 at the rear end of the passageway 46. A rearward cylindrical projection 50 formed on the valve member 48 abuts the rearward wall of the cap or sleeve member 32 to limit the rearward movement of the valve, and a coil spring 52 seats against this portion of the element 32 and serves to urge the valve member 4S toward closed position. Preferably the valve 43 is made of hardened tool steel and the hammer member 42 is also preferably made of the same material. The piston 40 by preference is made of case hardened tool steel. A steel ring 54 is fixedupon the stem 45 of the valve 48 and at certain points during the relative movement of the parts is adapted to seat against the O-ring seal 55, disposed within a recess in the piston, to effect a valve action controlling the passage of fluid through the passageway 44 from the pressure space 56 behind the piston. There is an axial passageway 58 in the forward end of the hammer 42 and radial passages 59 provide communication between the passageway S and the chamber 60 forwardly of the piston-hammer assembly. Where the passageway 58 opens into'the central piston chamber 43 a tapered valve seat 62 is formed which is`controlled bythe steel ball valve 63, the valve being urged forwardly toward closed position by means of the coil spring 64.

A coil spring 65 is compressed between the forward surface of the hammer 42 and the rearward surface of the anvil 15. This spring may be termed the piston return helper spring, the function of which in connection with the pressure gas will be described.

Secured within the forward chamber 60 in advance of the piston assembly, by means of the split rings 68 and 69., is the ball locating ring 70,` against the rear face of which a series of latch or detent balls 72 press. Angled forward and radial inward pressure is applied to this series of balls 72 by means of the hardened tool steel compression ring 75 which has a conical forward surface and which is continually urged forwardly by the series of compression springs 76 which are backed up by the adjustable compression ring 77 threaded into the first stepped portion 22 of the body member 11.

In order to prevent relative rotation of the piston with respect to the other parts, a key element 80 is fixed in the compression ring 77 and slides within a key slot 81 in the wall of the piston. The key slot S1 is of considerable length and provides communication with a vent passageway 82 which upon occasion communicates with a portion of the groove or thread 83 in the handlecap member 25.

An important feature of the configuration of the piston 40, for coaction with the balls 72, is the raised cylindrical cam surface 85 which is of somewhat greater diameter than the principal diameter of the piston. There is provided a slight shoulder 86 forming a depression behind the raised portion 85, and there is a more pronounced shoulder and depression 87 forwardly of the raised cam surface 85. As a preview of the relative positions of the balls 72 and these piston surfaces, it may be pointed out that the balls occupy the depression' or shoulder 87 in FIGURE l, the rearward station 86 in FIGURE 2, and the intermediate cylindrical surface of the raised portion in FIGURE 3 of the drawings.

Passing again to the rearward portion of the device, it will be seen that the container 30 has a reverse turned rearward neck portion 89 which fits around the neck of the capsule 35 and the configuration is such as to ensure a gas-tight joint aided by the pressure of gas within the chamber 90 formed in the container 30. Incidentally, this container 30 is preferably made of a somewhat pliable material such as a polyethylene plastic, and where permitted in the absence of any rm enclosure, is somewhat expansible under the internal gas pressure-when the latter is supplied from the capsule 35. The forward wall portion 92 of the container 30 has a series of radially projecting pins 95 which are preferably made of nylon cemented or otherwise secured to the wall of the container 30. Due to the provision of the groove or pocket 96 in the inner wall of the member 27, the wall portion 92 of the container 30 may expand outwardly and the pins 95 projected into the annular groove 99 formed in the inner wall of the handle-cap member 25. The grooves 99 are wider than the diameter of the pins 95 for a purpose which will be developed during the description of the operation of the device.

Rigidly carried by the sleeve member 27 are the hardened steel pins 100 which run in the pair of spiral grooves formed in the inner surface of the handle-cap member and by means of which the latter member can be screwed onto the body portion 11 during the installation of the capsule. In FIGURE 7 these grooves are clearly shown at 83 with an annular base groove indicated at 83'.

Operation The operation of the novel impact tool may be described as follows. With the handle-cap member 25 removed, an ordinary commercial compressed gas capsule or cartridge 35 is inserted therein with the sealed neck pointed forwardly. The handle-cap 25 is applied to the body portion 11 with the pins 100 fitted into the double internal thread grooves 83, 83' of the cap and rotated which will cause the cap to telescope forwardly upon the body of the implement. This will icause the piercing point 34 carried by the internal cap member 32 to-pierce the soft seal of the capsule or cartridge 35 thereby releasing compressed gas into the intermediate pressure supply chamber 90 within the container member 30.

The admitted gas pressure will deform the thin wall 92 of the container member 3() which carries the locking pins 95. These pins will thereupon project into the ring groove 99 of the cap member 25 and prevent the removal of the cap during the time that any gas pressure is present within the chamber 9i) in the container 30.

The gas pressure extending past the main valve 48 through the axial passageway 46 in the rear wall of the body member 11 expands into the chamber 56 rearwardly of the piston 40 and exerts a forward thrust on the piston which, when of sufficient force to overcome the spring pressure of the balls 72 resting against the forward shoulder 87 of the piston, will force the piston 40 forwardly.

The piston travel is then limited by the hammer member 42 abutting the rear portion 16 of the anvil 15 carried by the tool head shank 13.

Assuming that the tool head is not pressed against the work at this time, and the anvil occupies the forward portion of the groove or recess 20 due to the pressure of the spring 65, the piston and hammer assembly lwill travel far enough to permit the balls 72 to pass over the cylindrical surface of the raised cam portion and drop into the small rearward recess 86 on the surface of the piston. This obstacle, although slight, -is sufficient so that it cannot be overcome by either the pressure of the helper spring 65 or what gas pressure has been permitted to escape into the forward chamber 60 of the tool due to the opening of the Icheck valve 63 by being prodded by the projection 17 on the rearward portion ofthe anvil.

Now by this time the main supply uid pressure control valve 48 has closed, preventing any additional gas pressure to accumulate in the chamber 56 behind the piston.

The above description has carried through the positions shown in FIGURE 1 and up to the cocked position of the device as' shown in FIGURE 2 of the drawings. In this position the tool is now in condition for operation either as a repeater device or for delivering a single blow. This position is also the same as if the device were removed from the work during any normal operation thereof.

Next, the point or head of the tool carried upon the shaft or shank 13 is applied to the solid work surface against which the impact is to be delivered. This pressure of course is applied by pressing manually on the rear end of the handle portion 25 of the tool, and causes two principal motivating events to happen to the mechanism.

First, the capsule neck is moved forwardly until the valve surfaces 36 and 33 contact and the fluid pressure Within the capsule 35 is sealed off from the intermediate fluid pressure supply chamber 9tl'within the container 30. Thus, during the time that the handle-cap member is pressed forwardly, reliance must `be placed upon the accumulated pressurein the chamber for operation of the tool.

Secondly, the application of the tool to the workcauses the anvil 15 carried by the shank 13 to move rearwardly within the space 20 until it abuts the shoulder bounding this space. This causes the piston to move sufciently in a rearward direction to cause the balls 72 to ride over the rearward shoulder 86 and up upon the major cylindrical surface S5 of the cam configuration on the piston surface; and with this obstruction removed, and with helper spring 65 compressed to a certain added degree, the latter spr-ing is now sufficiently strong to move the piston all the way back.

During the above described portion of the movement of the device, the parts shift from the positions shown in FIGURE 2 to those shown in FIGURE 3 just before the spring 65 starts the piston toward its full rearward travel.

Now from the position shown in FIGURE 3 the piston moves all the way rearwardly carrying with it the valve 48 which moves from the seat 49 and Huid pressure is again admitted from the chamber 90 within the container 30 to the working chamber 56 rearwardly of the piston. It is also to be mentioned that when the parts move from the position shown in FIGURE 3 to that of FIGURE 4, the seal valve parts 54 and 55 come together and also the ball check valve 63 resumes its seat. This prevents the pressure bypassingr the piston and the full force of the gas pressure admitted to the chamber 56 drives the piston forwardly until the hammer portion 42 delivers a blow to the end portion 16 of the anvil 15 and causes the tool head carried by the shank 13 to impact the work.

If it is desired to deliver only one blow, the handle cap 25 is released and retracted and the tool removed from the work whereupon the anvil moves forwardly and the parts retreat to the idle position shown in FIGURE 1 of the drawings.

leiowever, if repeater action is desired, pressure is continued upon the handle and against the work and the gas pressure is cut off by the valve 48 and the remaining pressure in the chamber 56 is dissipated through the internal piston chambers and past the check valve 63 into the forward chamber 6l); whereupon this pressure, together with the pressure of the spring 63, returns the piston to the far right position shown in FIGURE 4. Thus, the tool will deliver a series of blows passing quickly from the positions of FIGURE 4 to those in FIGURE 3 and back to those of FIGURE 4 continually until all of the gas pressure in the supply cham-ber 9G is exhausted. Of course, as long as forward pressure is maintained, no further gas can escape from the cartridge or capsule 35 and the reciprocating repeat-impacting cycle is therefore limited by the amount of compressed gas available in the chamber 90. However, relieving of the pressure against the handlecap 25 momentarily will return the cap to the right, open the cartridge orifice, replenish the supply lin chamber 90, and a new cycle of repeat 4action can start.

It is to be noted that since downward or forward pressure on the tool can only be accomplished by pushing the cap forwardly or toward the left in the gures of drawing, the -cap will slide in relation to the tool body. This motion is permitted bythe width of the internal threads 83 in which the pins 100 move and also the width of the groove or undercut 99 into which the pins 95 project. The motion of course is limited by the cartridge neck surface 36 sealing against the surface 33 of the member 32.

When all usable pressure from the capsule is exhausted, the cap will not return or back off under gas pressure but will give a loose feeling to the hand of the operator. The pins 95 will thereupon have retracted by the deformation of the container 30 thus permitting the unscrewing of the cap and the removal of the spent cartridge or capsule.

The impacting force can be selectively varied by altering the tension-of the compression springs 76 which may be accomplished in the following manner. The nose 12, together with the anvil 15 and spring 65, is removed by unscrewing it from the body portion 11. A slot 110 is cut across the face of the hammer 42 and a screw-driver or other bladed tool can be applied thereto and the hammer and the axed piston unscrewed from the -body por.- tion. The key which slides in the keyway of the piston but is fixed in the compression adjustment ring 77, will transfer this rotary motion to the ring 77 which is threaded into the body 11. Turning the piston clockwise will screw the ring 77 to the right thereby reducing tension on the compression spring 76 which in turn will reduce the force necessary to force the balls 72 against the piston surfaces. Of course, a counterclockwise rotation will cause the tightening of the springs 72 and thus the increasing of the release pressure.

In order to bleed off the compressed gas from whatever side of this piston should be free of an air-cushion at any given point in the cycle of operation, the vent passageway 82 is alternately placed in communication with the working chamber 56 above the piston and, through the key-slot 81, with the chamber 60 beneath or n front of the piston. The passageway 82 vents into the grooves 83, 83 mainly, but the slight amount of pressure gas vented can escape even when the opening S2 does not immediately register with these grooves due to the non-air-ight lit of the handle cap 25 on the body 11.

It is understood that various changes and modifications may be made in the embodiment illustrated and described herein without departing from the scope o f the invention as dened by the following claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. An impact tool of the class described comprising, in combination, a tubular body; an impact head; a shank carrying said impact head at its outer end, entering the forward end of said body, and having a rearward terminal within said body constituting an anvil; a hammer device independently reciprocatable within a forward portion of said tubular body from a position in which it is spaced rearwardly of said anvil to a position where it is in impacting Contact with said anvil to cause the impact head to deliver a blow to' the work, and vice versa; a compressed gas chamber within a rearward portion of said body; a partition between said forward and rearward portions of the body, an opening in said partition, and a valve controlling said opening for applying gas under pressure from said chamber to the rearward end of said hammer device to propel it forwardly to strike said anvil; a source of compressed gas embodied within said tool, and a second valved opening controlling ow from said source for replenishing said compressed gas chamber from said source when needed; a rearwardly disposed handle telescoping with said body and having limited axial movement with relation to said body and means actuated by movement of the handle to open and close said replenishing valve opening.

2. An impact tool of the class described comprising, in combination, a tubular body; an impact head; a shank carrying said impact head at its outer end, entering the forward end of said body, and having a rearward terminal within said body constituting an anvil; a hammer device independently reciprocatable within a forward portion of said tubular body from a position in which it is spaced rearwardly of said anvil to a position where it is in impacting contact with said anvil to cause the impact head to deliver a blow to the work, and vice versa; a compressed gas chamber within a rearward portion of said body; a partition between said forward and rearward portions of the body, an opening in said partition, and a valve controlling said opening for applying gas under pressure from said chamber to the rearward end of said hammer device to propel it forwardly to strike said anvil; said hammer device comprising a pneumatic piston fitted into a working chamber in said body and provided with a hammer portion at its forward end; valve controlled by-pass means leading through the piston from one end to the other; means opening said by-pass means toward the end of the forward impact movement of the piston to permit a portion of the compressed propelling gas to ow to the forward end of the piston to assist the return or retractive movement of the piston; and means controlled by the forward movement of the piston to cause the first named valve to cut olf the supply of gas from said compressed gas chamber.

3. The impact tool as set forth in claim 2 in which a compression spring is applied against the forward end of said piston to urge it rearwardly toward retracted position in conjunction with the force of the by-passed gas; and in which latching means are provided for yieldably retaining said piston in its respective forward or retracted positions.

4. The impacting tool as set forth in claim 3 in which the anvil is disposed for limited axial movement in the body, and said compression spring is disposed between said anvil and said piston for exerting variable retractive lforce on the piston depending on the position of the anvil; the yieldable latching means tending to hold the piston in forward projected position being relatively weak so as to yield and release the piston for retraction when the anvil is moved rearwardly to further com-- press said spring as upon pressing the impact head against the work.

5. The impact tool as set forth in claim 3 in which said latching means comprises spring-pressed means exerting continual pressure radially inwardly toward the piston, and an annular rib on the outer surface of the piston having a forward shoulder in front of which said springpressed means lodges when the piston is in its rearward position, and a rearward shoulder behind which said spring-pressed means lodges when the piston is in its forward position.

6. The impact tool as set forth in claim 5 in which there is provided a fixed annular shoulder on the interior wall or said hollow body, and an abutment ring axially movable relatively to said shoulder, said spring-pressed means comprising an annular series of balls seized between said shoulder and said abutment ring, the ball-contacting surfaces of said shoulder and said ring diverging radially inwardly to produce a resultant force to urge the balls toward the piston; a backing annulus on the interior wall of said tubular body and axially spaced from vsaid abutment ring, springs disposed behind said ring and compressed between said ring and said backing annulus; and means for adjusting the position of said annulus to vary the pressure exerted by said springs and thus the force required to displace the latch balls and propel the piston and hammer device.

7. The impact tool as set forth in claim 5 in which the forward shoulder on the rib is deeper than the rearward shoulder, whereby less force is required to move this piston rearwardly than to propel it forwardly.

8. An impact tool of the class described comprising, in combination, a tubular body; an impact head; a shank carrying said impact head at its outer end, entering the forward end of said body, and having a rearward terminal within said body constituting an anvil; a hammer device independently reciproc'atable within a forward portion of said tubular body from a Iposition in which it is spaced rearwardly of said anvil to a position where it is in impacting contact with said anvil to cause the impact head to `deliver a blow to the work, and vice versa; a compressed gas chamber within a rearward portion of said zbody; a partition between said forward and rearward portions of the body, an opening in said partition, and a valve controlling said opening for applying gas under pressure from said chamber to the rearward end of said hammer device to propel it forwardly to strike said anvil; accommodation provided in said body for limited axial movement of said anvil; a compression sprng seated between the rearward face of said anvil and the forward face of said hammer device; retaining means tending to keep the hammer device in its forward position, and effective to do so when the anvil is at its forward limit of movement with said compression spring relatively relaxed, but being of such limited resistance as to be overbalanced by the urging of said compression spring `when it is additionally compressed by movement of the anvil to its rearward limit of movement.

9. The impact tool asset forth in claim 3 in which a valved by-passpassageway is formed in the hammer device and means for opening said passageway for ow of pressure gas to the forward face of the hammer device toward the end of its forward movement in order to supplement the force. of said compression spring to return the hammer device to retracted position.

10. The impact tool as set forth in claim 9 in which the by-pass passageway valving comprises a springpressed check valve controlling an axial passageway in the forward end of the hammer device anda projection extending rearwardly from said anvil for pressing said valve to open position toward the end of the stroke of the hammer device.

11. The impact tool as set forth in claim 10 in which there are provided passageways in said body controlled by the position -of the hammer device to vent either the space ahead of the hammer device or the space behind it to the atmosphere.

12. An impact tool of the `class described comprising, in combination, a tubular body; an impact element telescoping into the forward end of saidbody, pneumatically actuated means in said body for causing said impact element to deliver a blow to a piece of work to which it is applied, a compressed gas chamber within'said body for containing a supply of gas for operating said pneumatic actuating means for a cycle of repeated impacts; a compressed gas cartridge carried within said body and having a puncturable closure, and means for piercing said closure and also effecting an adjustable valving of the opening in the cartridge thus formed, and means for moving said piercing and valving means at will to replenish the supply of compressed gas in said chambe for another cycle of operation.

13. An impact tool of the class described comprising, in combination, a tubularvbody; :an impact element tele'- scoping into the forward end of said body, pneumatically actuated means in said body for causing said impact element to deliver a blow to a piece of work to which it is applied, a compressed gas chamber within said body for containing a supply of gas for operating said pneumatic actuating means for a cycle `of repeated impacts; a source of compressed gas carried by said tool, and means for tapping said source at will to replenish the supply of pressure gas in said chamber for another cycle, a hollow handle member mounted for relative telescoping movement with respect to the rearward portion of the body and contains said source, and valve means is provided for opening and closing communication with said source upon axial movement of said handle.

14. The impact tool as set forth in claim 13 in which means is provided for interlocking said hollow handle.

, tion on said chamber, and a pin carried by said expansible vvall portion in registry kwith said socket, whereby whenever there is gas pressure in said chamber the pin will be projected into said socket.

16. The impact tool as set forth in claim 15, in which' the dimension of said pin longitudinally of the tool is smaller than the corresponding dimension of said socket to allow `for limited valve actuating movement of the handle to tap the source of gas pressure.

17. The impact tool as set forth in claim 16 in which the inner surface of the sleeved handle is provided with at least one screw-thread groove leading through the forward end thereof, and a pin fixed to a portion of said body enters said groove whereby the handle may be screwed onto and removed from said body, the last named pin being of less dimension longitudinally of said tool than the screw-thread groove to permit lost motion -when the handle is moved longitudinally to actuate the gas source valving.

18. The impact tool as set forth in claim 13 in which the inner surface of the sleeved handle is provided with at least one screw-thread groove leading through the forward end thereof, and a pin fixed to a portion of said body enters said groove whereby the handle may be screwed onto and removed from said body, the last named pin being of less dimension longitudinally of said tool than the screw-thread groove to permit lost motion when the handle is moved longitudinally to actuate the gas source valving.

19. The impact tool as set forth in claim 18 in which there are provided retaining means for preventing removal of said handle by unscrewing the same from said body, said retaining means having a degree of lost motion to permit the handle to function as described, and means subject to gas pressure in said chamber to -move said retaining means to and from operative and inoperative positions.

20. An impact tool of the class described comprising, in combination, a tubular body; an impact head; a shank carrying said impact head at its outer end, entering the forward end of said body, and having a rearward terminal within said body constituting an anvil; a hammer device independently reciprocatable within said tubular body from a position in which it is spaced rearwardly of said anvil to a position lwhere it is in impacting contact with said anvil to cause the impact head to deliver a blow to the work, Vand vice versa; a compressed gas chamber within said body; a main valve operable to admit gas pressure from said chamber to the rearward face of said hammer device, said hammer comprising a pneumatic piston fitted' into a working chamber in said body and provided with a hammer portion at its forward end; a passageway leading through the piston from one end to the other; a spring-pressed second valve in the forward end of said passageway, and a projection extending from the rear face of said anvil to unseat said valve toward the end of the forward impact movement of said piston to permit a portion of the compressed propelling gas to ow to the forward end of the piston to assist the return or retractive movement of the piston.

21. The impact tool as set forth in claim 20 in which said main valve is provided with a solid stem telescoping within said piston passageway, said stem having an annular shoulder portion of greater diameter than said passageway whereby the return movement of said piston moves said stem to open said main valve.

22. The impact tool as set forth in claim`21 in which said main valve stem lits Aloosely in said piston passageway, :and said shoulder and the margin of the opening of said passageway through the rearward face of the piston comprise cooperating valve parts to close said passageway fwhen in cont-act, in order to increase the effective driving pressure against the rear face of the piston.

23. An impact tool of the class described comprising, in combination, a tubular body; an impact head; a shank carrying said impact head at its outer end, entering the forward end of said body, and having a rearward terminal within said body constituting an anvil; a hammer device independently reciprocata-ble within said tubular body from a position in which it is spaced rearwardly of said anvil to a position where it is in impacting contact with said anvil to cause the impact head to deliver a blow to the work, and vice versa; a compressed gas chamber within said body; a main valve operable to admit gas pressure from said chamber to the rearward face of said hammer device, and a coil expansion spring disposed directly between the rear face of said anvil and the front face of said hammer to assist the return of the hammer, said hammer comprising a pneumatic piston fitted into a working chamber in said body and provided with a hammer portion at its forward end; a passageway leading through the piston from one en'd to the other; a spriugpressed second valve in lthe forward end of said passageway, and a projection extending from the rear face of said anvil to unseat said valve toward the end of the forward impact movement of said piston to permit a portion of the compressed propelling gas to ow to the forward end of the piston to assist the return or retractive movement of the piston.

References Cited by the Examiner UNITED STATES PATENTS 134,083 12/1872 McKay 173--121 1,665,046 4/ 1928 Tucker 173--132 2,290,256 7/1942 Souter 173-121 2,668,518 2/1954 White 173-121 3,104,395 9/1963 Grey et al 173--121 3,177,953 4/ 1965 Peterson 173--138 MILTON KAUFMAN, Primary Examiner. BROUGHTON G. DURHAM, Examiner. L. P. KESSLER, Assistant Examiner. 

1. AN IMPACT TOOL OF THE CLASS DESCRIBED COMPRISING, IN COMBINATION, A TUBULAR BODY; AN IMPACT HEAD; A SHANK CARRYING SAID IMPACT HEAD AT ITS OUTER END, ENTERING THE FORWARD END OF SAID BODY, AND HAVING A REARWARD TERMINAL WITHIN SAID BODY CONSTITUTING AN ANVIL; A HAMMER DEVICE INDEPENDENTLY RECIPROCATABLE WITHIN A FORWARD PORTION OF SAID TUBULAR BODY FROM A POSITION IN WHICH IT IS SPACED REARWARDLY OF SAID ANVIL TO A POSITION WHERE IT IS IN IMPACTING CONTACT WITH SAID ANVIL TO CAUSE THE IMPACT HEAD TO DELIVER A BLOW TO THE WORK, AND VICE VERSA; A COMPRESSED GAS CHAMBER WITHIN A REARWARD PORTION OF SAID BODY; A PARTITION BETWEEN SAID FORWARD AND REARWARD PORTIONS OF THE BODY, AN OPENING IN SAID PARTITION, AND A VALVE CONTROLLING SAID OPENING FOR APPLYING GAS UNDER PRESSURE FROM SAID CHAMBER TO THE REARWARD END OF SAID HAMMER DEVICE TO PROPEL IT FORWARDLY TO STRIKE SAID ANVIL; A SOURCE OF COMPRESSED GAS EMBODIED WITHIN SAID TOOL, AND A SECOND VALVED OPENING CONTROLLING FLOW FROM SAID SOURCE FOR REPLENISHING SAID COMPRESED GAS CHAMER FROM SAID SOURCE WHEN NEEDED; A REARWARDLY DISPOSED HANDLE TELESCOPING WITH SAID BODY AND HAVING LIMITED AXIAL MOVEMENT WITH RELATION TO SAID BODY AND MEANS ACTUATED BY MOVEMENT OF THE HANDLE TO OPEN AND CLOSE SAID REPLENISHING VALVE OPENING. 